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Abstract


Today the prevalent bone conduction (bc) audiometric transducer is the B-71 from Radioear Corporation, USA. This type of transducers suffer from some severe limitations with regard to low frequency response and distortion at high signal levels.

A new type of electro dynamic transducer for audiometric investigations named Balanced Electromagnetic Separation Transducer (BEST)
has been developed.

By using a balanced
suspension principle,
with opposing air gaps,
the quadratic distortion
forces as well as the
always existing biasing
magnetic forces are
cancelled.
The advantages with this new design has been verified in a number of laboratory tests on first series of prototypes.

Conclusively, from the laboratory
tests of the BEST performance compared with the conventional B-71 performance, it was found that:

  • BEST has considerably lower distortion over the entire frequency range.

  • BEST has a lower resonance frequency for a given counterweight mass.

  • BEST is more efficient.

These results imply that bc tests can be conducted at lower frequencies (down to 250Hz) and at higher levels than befor. In general terms one can say that a more severe sensorineural hearing losses can accurately be measured with the new transducer.